U.S. patent number 4,326,981 [Application Number 06/066,609] was granted by the patent office on 1982-04-27 for nonstaining leak tracer solution and method employing same.
This patent grant is currently assigned to Rockwell International Corporation. Invention is credited to Orlando G. Molina.
United States Patent |
4,326,981 |
Molina |
April 27, 1982 |
Nonstaining leak tracer solution and method employing same
Abstract
Leak tracer solution particularly effective for inspection of
aircraft fuel tanks and lines prior to use, without staining
painted surfaces of the aircraft consists essentially of an aqueous
solution containing not more than about 10%, generally about 0.1 to
about 10%, of a nonionic oxyalkylated aliphatic alcohol surfactant,
and a small amount, generally about 0.005 to about 1.0%, of a water
soluble, e.g. dual visibility, dye such as Uranine, which does not
migrate into or penetrate the painted aircraft surface. A small
amount of an anti-parasitic agent can be added to prevent algae
growth. The solution is used by introducing it into the interior of
new fuel tanks and lines, viewing the external surfaces of such
tanks and lines under suitable lighting conditions such as daylight
or black (fluorescent) light to detect any cracks or leaks, and
draining the solution from the tanks and lines. After such
draining, preferably a "depuddling" agent is introduced to
chemically blend any water-based leak tracer solution remaining in
depressions of the fuel tanks or lines, with the oil-based
aircraft's fuel, for removal of such remaining leak tracer
solution. A preferred "depuddling" agent is a 50-50 mixture by
volume of a petroleum-based aircraft fuel, and a nonionic
oxyalkylated aliphatic alcohol surfactant.
Inventors: |
Molina; Orlando G.
(Westminster, CA) |
Assignee: |
Rockwell International
Corporation (El Segundo, CA)
|
Family
ID: |
22070585 |
Appl.
No.: |
06/066,609 |
Filed: |
August 15, 1979 |
Current U.S.
Class: |
252/301.19;
73/104 |
Current CPC
Class: |
G01M
3/20 (20130101); C09D 5/22 (20130101) |
Current International
Class: |
C09D
5/22 (20060101); G01M 3/20 (20060101); C09K
011/06 () |
Field of
Search: |
;252/408,301.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Edmundson; F.
Attorney, Agent or Firm: Silberberg; Charles T. Geldin;
Max
Claims
What is claimed is:
1. A leak tracer solution consisting essentially of a major
proportion of water, about 0.1 to about 10% by weight of a nonionic
surfactant, and about 0.005 to about 1.0% by weight of a water
soluble dye which is essentially non-staining on painted surfaces,
and which does not migrate into or penetrate painted surfaces, said
painted surfaces containing a polyurethane or epoxy resin base,
said nonionic surfactant being of the group consisting of (a)
straight chain, primary, aliphatic oxyalkylated alcohol, wherein
said alcohols can contain from 8 to 20 carbon atoms and the
oxyalkyl groups are ethylene oxide and propylene oxide groups, and
(b) ethoxylates of linear secondary aliphatic alcohols, with the
hydroxyl groups randomly distributed, the linear aliphatic portion
of said alcohols being a mixture of alkyl chains containing in the
range from 10 to 17 carbon atoms, and containing an average of from
3 to 12 moles of ethylene oxide.
2. The leak tracer solution as defined in claim 1, said surfactant
being present in an amount ranging from about 0.3 to about 2.0% by
weight.
3. The leak tracer solution as defined in claim 2, said dye being
present in an amount ranging from about 0.01 to about 0.10% by
weight.
4. The leak tracer solution as defined in claim 3, wherein said
surfactant consists of ethoxylates of a mixture of alcohols having
the formula: ##STR3## where n is in the range from 9 to 13 and m is
an average of 3 to 12.
5. The leak tracer solution as defined in claim 1, said dye being
selected from the group consisting of water soluble uranine,
rhodamine and eosin dyes.
6. The leak tracer solution as defined in claim 1, wherein said dye
is a fluorescent dye.
7. The leak tracer solution as defined in claim 1, wherein said dye
is a dual visibility uranine dye.
8. The leak tracer solution as defined in claim 1, wherein said
surfactant (a) is a mixture of compounds having the formula:
wherein R is an essentially linear alkyl group having from 10 to 18
carbon atoms, at least 70 weight percent of said compounds in said
mixture having an R of from 12 to 16 carbon atoms, and A is a
mixture of oxypropylene and oxyethylene groups, said oxypropylene
and oxyethylene groups being from 55 to 80% of the total weight of
said compounds, the oxypropylene to oxyethylene ratio of said total
weight being from 0.85:1 to 2.75:1, and wherein said surfactant (b)
are ethoxylates of a mixture of alcohols having the formula:
##STR4## where n is in the range from 9 to 13 and m is an average
of 3 to 12.
9. The leak tracer solution as defined in claim 8, wherein R in
said surfactant (a) can have from 12 to 18 carbon atoms, and the
total number of A groups can range from about 4 to about 14; and
wherein in said surfactant (b) the linear alkyl hydrophobic portion
of said surfactant is a polyoxyethylene chain randomly attached to
the linear alkyl hydrophobic chains through an ether linkage, and
wherein said surfactant (b) is selected from the group consisting
of said ethoxylates of said mixture of alcohols, wherein n ranges
from 9 to 13, and m is an average of 3, 5, 7, 9 or 12.
Description
BACKGROUND OF THE INVENTION
This invention relates to an improved leak tracer composition or
solution for detecting leaks, particularly in the fuel tanks and
lines of aircraft, and is particularly concerned with an inproved
leak tracer solution of the above type, and which does not adhere
to external surfaces contacted by the leak tracer, and which does
not stain the painted, and particularly white painted, surfaces of
the aircraft.
Newly fabricated fuel tanks and lines for aircraft are generally
tested for cracks and leaks before installation in the aircraft,
utilizing a leak tracer solution. Such leaks tracer solutions
heretofore employed usually consist of water, a detergent, glycerin
and a dye, usually a red dye.
However, when employing such conventional leak tracer solutions,
the red dye contained in the leak tracing solution tended to
permanently stain the white painted surfaces of the aircraft if a
spill or leak occurred. Such painted surfaces can be the exterior
surfaces of the suel tanks, or other adjacent surfaces of the
aircraft such as the wings or other components. Further, a film of
the glycerin contained in the formulation adhered to all surfaces
contacted by the leak tracer. Also, there were algae-like
substances bearing the color of the leak tracer found entrapped in
and clogging certain passages of the aircraft's fuel system, and
some of the leak tracer solution remained entrapped or "puddled" in
depressions and low areas of the fuel tanks and lines. Careful and
repeated cleaning was thus necessary until all of the spilled and
remaining leak tracer solution was removed, and clogging fuel lines
were freed of the leak tracer solution.
Dye penetrant compositions containing nonionic oxyalkylated alcohol
surfactants, derived from both primary and secondary aliphatic
alcohols, as vehicle, and a dye, are described in my U.S. Pat. Nos.
3,915,885 and 3,915,886. These, however, are non-aqueous solutions
which are applied to the external surfaces of test bodies or parts
to detect surface flaws or cracks therein by retention of dye
penetrant in such cracks and flaws, and by viewing such retained
dye entrapments under suitable lighting conditions.
Accordingly, an object of the present invention is the provision of
an improved leak tracer composition or solution particularly
designed for fuel tanks and lines. A further object of the
invention is to provide a leak tracer solution of the above type
which does not stain the painted, and particularly white painted,
surfaces of aircraft. A still further object of the invention is to
provide a novel water-based leak tracer solution which does not
contain substances such as glycerin which tend to adhere to the
interior surfaces contacted by the leak tracer solution, and which
do not promote parasitic growth which clog passages, e.g. in
aircraft fuel systems. Another object is to provide a simple,
inexpensive, highly penetrating and essentially water-based leak
tracer solution of the above type, containing a minimum of readily
available components. A further object is to provide procedure for
detection of cracks and leaks, particularly in aircraft fuel tanks
and lines, employing the above leak tracer solution.
SUMMARY OF THE INVENTION
The above objects and advantages are achieved according to the
invention by employing as a leak tracer solution a composition
consisting essentially of water, a nonionic oxyalkylated aliphatic
alcohol surfactant, and a small amount of a dye which is
essentially non-staining on painted surfaces.
As described more fully hereinafter, the leak tracer solution of
the invention contains a major proportion of water, not more than
about 10% of a nonionic oxyalkylated aliphatic alcohol surfactant,
and generally about 0.005 to about 1.0% by weight of such water
soluble essentially non-staining dye.
A small amount of an anti-parasitic agent is added to the leak
tracer solution to inhibit parasitic algae growth in the
solution.
As a feature of the invention, the leak tracer composition or
solution hereof is free of glycerin and does not adhere to the
surfaces such as the interior surfaces of fuel tanks and lines
contacted by the leak tracer solution. Further, the "creepability"
characteristics, relating to the ability of the leak tracer
solution to penetrate into and aid in the detection of cracks and
leaks in fuel tanks and lines, is superior in the case of the leak
tracer of the present invention, as compared to the heretofore
employed glycerin-based leak tracer. Also, the leak tracer of the
present invention employing particularly certain water-soluble dyes
which do not migrate or penetrate into the painted surfaces of
aircraft, do not stain the generally white painted surfaces of the
aircraft, usually containing a polyurethane or epoxy resin
base.
Following introduction of the leak tracer solution into fuel tanks
and fuel lines of aircraft for detection of leaks therein, the leak
tracer solution is removed and any leak tracer solution which is
entrapped or puddled in low areas and crevices in the fuel tanks
and lines can be removed by introduction of a solution or
"depuddling" agent which is miscible with the aqueous leak tracer
solution and also with the petroleum-based aircraft fuel, so that
the aircraft fuel subsequently introduced into the fuel tanks and
lines can then be used to flush out such remaining pockets of
entrapped leak tracer solution after it is mixed with depuddling
agent.
The water-based leak tracer solution of the present invention
cannot wet previously fuel-wetted surfaces of fuel tanks and lines,
and therefore cannot penetrate and disclose leak paths in such
fuel-wetted surfaces. Thus the leak tracer solution of the present
invention is applicable for use in detecting cracks and leaks only
in newly fabricated and dry fuel tanks and lines which require leak
detection inspection.
DETAILED DESCRIPTION AND EMBODIMENTS OF THE INVENTION
The nonionic surfactants which are incorporated into the aqueous
leak tracer solutions or compositions of the invention consist
essentially of an oxyalkylated aliphatic alcohol or mixtures
thereof, formed of an aliphatic primary or secondary alcohol
carrying ethoxy or propoxy groups, including polyoxyethylene or
polyoxypropylene groups, or mixtures thereof.
More particularly, one class of such nonionic surfactants can be
defined as straight chain, primary, aliphatic oxyalkylated
alcohols, generally in the form of mixtures thereof, wherein the
primary aliphatic alcohols can have from 8 to 20 carbon atoms,
preferably 10 to 18 carbon atoms, and the oxyalkyl groups are
ethylene oxide and propylene oxide, preferably in the form of a
mixture thereof.
One group of nonionic surfactants within the class of materials
defined immediately above is a cogeneric mixture of compounds
represented by the formula:
wherein:
R is an essentially linear alkyl group having from 10 to 18 carbon
atoms, with the proviso that at least 70 weight percent of said
compounds in said mixture have an R of from 12 to 16 carbon atoms,
and A is a mixture of oxypropylene and oxyethylene groups, said
oxypropylene and oxyethylene groups being from 55% to 80% of the
total weight of the compounds, the oxypropylene and oxyethylene
ratio of said total weight being from 0.85:1 to 2.75:1, preferably
1.25:1 to 2.25:1.
Another preferred class of condensation products or oxyalkylated
alcohols within the above definition are those wherein the
aliphatic alcohols of the oxyalkylated alcohols, or R in the above
formula, ranges from 12 to 18 carbon atoms, and the total number of
ethylene oxide and propylene oxide groups in the mixture thereof,
or designated A in the above formula, ranges from about 4 to about
14.
The term "cogeneric mixture" as employed herein, designates a
series of closely related homologues obtained by condensing a
plurality of oxide units, with an alcohol or a mixture thereof. As
is shown, when a mixture of this type is generated, various
oxyalkylene chain lengths are obtained.
Alcohols which may be employed in the preparation of the products
noted above are those essentially linear, primary, aliphatic
alcohols having from 8 to 20 carbon atoms, preferably 10 to 18
carbon atoms. Mixtures of alcohols are usually preferred since
their use provides for a good balance of properties in the
resulting products. Examples of alcohols which are operable include
decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol,
tetradecyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl
alcohol, stearyl alcohol, hydrogenated tallow alcohol, and mixtures
thereof. They may be naturally-derived such as from coconut oil or
synthetically-derived such as from linear alkanes or linear
olefins.
The above nonionic surfactants employed in conjunction with the dye
of the leak tracer solution according to the invention, are
prepared by condensing an alcohol or mixture of alcohols, as
described above, with a mixture of ethylene oxide and propylene
oxide, in the presence of an alkaline catalyst, such as potassium
hydroxide. The oxide mixture may be added to the alcohol in one
continuous step or it may be added in several steps. The products
thus produced possess random distribution of oxyethylene and
oxypropylene groups.
The nonionic surface active agents described above and their method
of preparation are disclosed in U.S. Pat. No. 3,504,041, and such
disclosure is incorporated herein by reference. These surface
active agents are believed to include for example, that class of
surfactants which are marketed as the "Plurafac" surfactants
"RA-40" grades.
Another class of biodegradable liquid, water miscible oxyalkylated
alcohol condensation products within the above definition are those
wherein the aliphatic alcohol, or R, is a straight chain alkyl
group having from 8 to 20 carbon atoms, the number of ethylene
oxide groups in the mixture thereof with propylene oxide, or A
ranges from 3.75 to 12.75, and the number of propylene oxide groups
in such mixture ranges from 1.7 to 7.0, the oxyethylene to
oxypropylene ratio in such mixtures being from 1.8:1 to 2.2:1. This
mixture of condensation products and the method of their
preparation are disclosed in U.S. Pat. No. 3,340,309, and such
disclosure is also incorporated herein by reference. The nonionic
oxyalkylated alcohols marketed as the "RO-20" grades of "Plurafac",
are believed representative of the class of surface active agents
disclosed in the latter patent.
Various other "Plurafac" grades which are marketed and are believed
to be generally within the above-described classes of oxyalkylated
alcohol surfactants are those designated RA-43, A-24, A-25, B-25-5,
B-26 and D-25.
Dye penetrant compositions containing the above described primary
aliphatic oxyalkylated alcohols as vehicle, and a dye are described
in my U.S. Pat. No. 3,915,885.
A class of particularly preferred nonionic biodegradable
surfactants which can be employed in the leak tracer compositions
according to the present invention are ethoxylates of a mixture of
linear secondary aliphatic alcohols, with the hydroxyl groups
randomly distributed, the linear aliphatic hydrophobic portion of
such alcohols being a mixture of alkyl chains containing in the
range from 10 to 17 carbon atoms, preferably from 11 to 15 carbon
atoms, and containing an average of from 3 to 12 moles of ethylene
oxide.
The above particularly preferred class of ninionic biodegradable
surfactant employed according to the invention is a mixture of
compounds which can be represented by the formula: ##STR1## where n
is in the range from 9 to 13, and m is 3 to 12.
Although preferably each of the above-defined surfactants is formed
of a mixture of two or more linear alkyl hydrophobic chains ranging
from C.sub.11 to C.sub.15, as noted below, the surfactant can
contain a single such chain formed from a single secondary
aliphatic alcohol of the types described below.
The linear alkyl hydrophobic portion of the above defined
surfactant is a mixture of C.sub.11 to C.sub.15 linear alkyl
chains, and can be derived from a mixture of C.sub.11 to C.sub.15
aliphatic secondary alcohols, for example the secondary undecyl,
dodecyl, tridecyl, tetradecyl and pentadecyl alcohols. The
hydrophilic portion of the surfactant is a polyoxyethylene chain
randomly attached to any carbon atom of the linear alkyl
hydrophobic chains, other than to the terminal carbon atoms
thereof, through an ether linkage. It will accordingly be
understood that the specific carbon atom in the alkyl hydrophobic
chains to which the hydrophilic polyoxyethylene chain is attached
will become a ##STR2## group. Such hydrophilic polyoxyethylene
chain is generally expressed in terms of an average number of moles
of ethylene oxide.
Illustrative examples of biodegradable nonionic surfactants of the
types defined in the above formula are those consisting of a
mixture of ethoxylates of from 11 to 15 carbon atoms in the
aliphatic hydrophobic chain, and which have an average of 3, 5, 7,
9 and 12 moles of ethylene oxide, respectively, as the
hydrophil.
Materials corresponding to these five examples of biodegradable
nonionic surfactants are marketed, respectively, as:
______________________________________ Tergitol 15-S-3 " 15-S-5 "
15-S-7 " 15-S-9 " 15-S-12
______________________________________
In each case of the Tergitol S series of surfactants listed above,
the number to the left of the "S" indicates a hydrophobic aliphatic
chain of from 11 to 15 carbon atoms derived from a mixture of
alcohols on C.sub.11 to C.sub.15 backbone chains, and the number to
the right of the "S" designates the average number of moles of
ethylene oxide as the hydrophil. Thus, for example, Tergitol 15-S-5
is a mixture of linear aliphatic alcohols in the C.sub.11 to
C.sub.15 range ethoxylated with an average of 5 moles of ethylene
oxide. All of these commercially marketed Tergitol S series of
surfactants are water soluble except for Tergitol 15-S-3, which is
essentially water insoluble. Mixtures of these materials can also
be employed in providing the dye penetrant of the invention, such
as a mixture of the above Tergitols 15-S-5 and 15-S-3; a mixture of
15-S-3 and 15-S-9; and a mixture of 15-S-5 and 15-S-9.
The above preferred class of nonionic biodegradable surfactants
employed in the leak tracer solution according to the invention,
are prepared by reacting an alcohol or mixture of alcohols, with
the desired proportion of ethylene oxide, in the presence of an
alkaline catalyst, such as potassium hydroxide. The ethylene oxide
may be added to the alcohol or mixture of alcohols in one
continuous step or it may be added in several steps. The products
thus produced possess random distribution of oxyethylene groups, as
noted above.
Another process for preparing the above nonionic surfactants in the
form of ethoxylates of linear secondary aliphatic alcohols, is
described in U.S. Pat. No. 2,870,220.
Tergitol 15-S-3 is essentially water insoluble and is usually
employed in combination with the other members of the Tergitol S
series noted above, such as Tergitol 15-S-5 and 15-S-9.
Dye penetrant compositions containing the above described
ethoxylates of secondary aliphatic alcohols as vehicle and a dye
are described in my U.S. Pat. No. 3,915,886.
Also, particularly effective leak tracer solutions are provided
according to the invention employing a combination or mixture of
the above Tergitols 15-S-5 and 15-S-9, and to which there can be
added optionally Tergitol 15-S-3, as described in my U.S. Pat. No.
3,939,092.
There can also be employed ethoxylates of linear primary alcohols,
corresponding to the ethoxylates of the linear secondary alcohols
of the Tergitol S series of nonionic surfactants described above.
Thus, the Tergitol 25-L series of nonionic surfactants is derived
by ethoxylation of a blend of C.sub.12 to C.sub.15 linear primary
alcohols, the soluble derivatives of which contain from about 5 to
about 9 moles of ethylene oxide, per mole of primary alcohol.
The dyes which are incorporated into the leak tracer compositions
or solutions of the invention are water soluble dyes which can be
either daylight visible dyes or fluorescent dyes made visible by
exposure to black or fluorescent light, or such dyes can have dual
visibility, that is, they are visible either in daylight or are
fluorescent under black or fluorescent light. Such dyes are of a
type which do not migrate into or penetrate painted surfaces used
on aircraft, such as white polyurethane paints.
Preferred dyes which can be used are the water soluble uranine,
rhodamine and eosin dyes.
A preferred water soluble uranine dye having the characteristics
noted above is Uranine Concentrate 1801 dye, Color Index Yellow 73,
marketed by Keystone, Ingham Co., Los Angeles, California. This dye
is a sodium salt of fluorescein, and is a yellow-green dual
visibility dye visible by exposure either to daylight or
fluorescent light.
The soluble rhodamine dyes such as Rhodamine B, Rhodamine-Color
Index 10 and Rhodamine WT-Color Index Acid Red 388 can be used.
These are also dual visibility dyes. Rhodamine dyes tend to stain
painted surfaces, but can be used in leak tracer solutions on
equipment such as fuel tanks and lines which have not yet been
installed in already painted aircraft. For this reason rhodamine
dyes are not preferred dyes for use in the leak tracer solutions of
the invention.
The eosin dyes such as Eosin G and Eosin Acid Red 87 also can be
used, particularly in the form of their sodium or potassium salts.
The eosin dyes are fluorescent dyes which are made visible by
exposure to black or fluorescent light.
Water is employed in major proportions in the leak detector
solution of the invention. Although tap water can be employed, the
water used should be as free as possible from residue forming
materials such as minerals. Thus, distilled or deionized water can
also be used.
The amount of nonionic oxyalkylated surfactant which is
incorporated into the leak detector solution of the invention
should not be more than about 10% by weight of the composition.
Generally, from about 0.1 to about 10% by weight of the surfactant
is used. Although up to 20% by weight of the surfactant can be
used, this is uneconomical and is not preferred. It has been found,
however, that a low surfactant content, ranging from about 0.3 to
about 2.0% by weight of the leak tracer solution or composition
provides best results in improved "creepability" of the leak tracer
solution, that is, its ability to penetrate and detect very small
cracks and leaks in fuel tanks and lines.
The amount of dye which is incorporated into the leak detector
solution containing water and the above nonionic surfactant, to
produce the leak tracer composition of the invention, is generally
small, e.g. ranging from about 0.005 to about 1.0% by weight of the
composition. Preferably about 0.01 to about 0.10% by weight of the
dye is present in the leak tracer solution.
Optionally, a very small amount, e.g. a few drops, of an
anti-parasitic agent, per gallon of leak tracer solution, e.g. 8 to
12 ounces per 500 gallons, is incorporated in the leak tracer
solution to prevent parasitic algae growth in the solution,
particularly if it is stored over an extended period of time. A
typical anti-parasitic agent for this purpose is the material
marketed as "Clear Bath 105540" which is believed to be an amino
based composition, by Spectrum Medical Industries, Torrance, Calif.
However, any suitable alkaline anti-parasitic agent can be
employed.
An optimum leak tracer solution according to the invention is the
solution or composition A below.
______________________________________ COMPOSITION A Component
Percentage by Weight ______________________________________ Water
99.41 Tergitol 15-S-9 .56 Uranine Conc. 1801 Dye .03 "Clear Bath
105540" 8 to 12 ounce per (anti-parasitic agent) 500 gallons water
______________________________________
It will be noted that Composition A above has low surfactant
content, that is in the above noted preferred surfactant range of
0.3 to 2.0% by weight of the composition.
Another representative leak tracer solution, according to the
invention, is solution of Composition B below.
______________________________________ COMPOSITION B Component
Percentage by Weight ______________________________________ Water
94.97 Tergitol 15-S-9 5.0 Uranine Conc. 1801 Dye .03 "Clear Bath
105540" 8 to 12 ounces per (anti-parasitic agent) 500 gallons water
______________________________________
In table 1 below are set forth additional examples of leak tracer
compositions or solutions according to the invention.
TABLE 1 ______________________________________ Compositions (% by
weight) Component C D E F G H J
______________________________________ Water 99.65 99.57 99.26
98.94 95.93 94.97 99.41 Tergitol 15-S-9 0.3 1.0 Tergitol 15-S-5 0.4
4.0 5.0 75% Tergitol 15-S-5 and 25% Tergitol 15-S-9 0.7 Uranine
Conc. 1801 Dye 0.05 0.03 0.04 0.06 0.07 0.03 0.03 "Clear Bath
105540" (anti- parasitic agent) 8 to 12 ounces per 500 gals. water
Plurafac A-24 0.56 ______________________________________
It is also noted that compositions C, D, E, F and J are
illustrative of the preferred low surfactant content compositions
of the invention, containing not more than 2.0% surfactant by
weight, while compositions B, G and H, each containing more than
2.0% by weight of surfactant, are illustrative of the high content
surfactant leak tracer solutions of the invention.
Incorporation of a small amount of an anti-parasitic agent, as
noted above, particularly into those leak tracer solutions having a
low surfactant content controls and avoids formation of parasitic
algae-like growths in the leak tracer solution when stored for
substantial periods of time, e.g. up to about 30 days. However,
since the biodegradable non-ionic surfactants such as the Tergitols
noted above, are a known source of food for bacteria, the high
surfactant content leak tracer solutions according to the invention
tend to generate parasitic growth after periods of storage, even
when an anti-parasitic agent is incorporated therein.
Tests for leak tracer efficiency or creepability were carried out
as between a presently employed leak tracer solution containing
glycerin, described in Example 1 below, and two leak tracer
compositions of the invention, one being a high surfactant
composition represented by Composition B above, and the other being
a low surfactant content leak tracer as represented by Composition
A noted above.
In carrying out this test, to evaluate the efficiency of these leak
tracers, a fixture was employed in the form of a metal plate having
13 deep grooves inscribed therein. The plate is placed on a base
which serves the purpose of supplying a controlled amount of the
leak tracer to the base of the inscribed plate. The plate is
vertically positioned on the base, and as the plate contacts the
leak tracer to be tested, each of the grooves therein
instantaneously commences to serve as an exposed capillarity tube
to allow the leak tracer to travel upwards in the respective
grooves. This upward movement of the leak tracer solution, or its
creepability, is timed, and at the end of twenty seconds, the
creeping activity of the leak tracer has been exhausted or has come
to a stop. Under suitable lighting conditions for the respective
dyes of the leak tracers, such as black light illumination for
fluorescent dyes, a mark is made with a felt tip pen at the upper
end of travel of the leak tracer solution in the respective
grooves. The measurements for the respective grooves on a single
plate for each of the respective leak tracers was totalled and
averaged. A set of three complete tests for a single leak tracer is
considered sufficient. A comparison of these measurements between
the above noted three leak tracers provides a quantitative rating
as to the creepability or efficiency of the respective leak tracer
solutions.
The creepability data and results for the three above noted leak
tracer solutions is set forth in Table 2 below.
TABLE 2 ______________________________________ LEAK TRACER SOLUTION
CREEPABILITY TEST Measurements of Upward Linear Creepability
Generated In 20 Seconds by Leak Tracer Solutions Each Submitted to
Three Separate Tests - Totalling 39 Observations Water Based Lowest
Highest Fluorescent Averaged Averaged Average of the Leak Tracers
Reading Reading 39 Readings Tested (Inches) (Inches) (Inches)
______________________________________ Leak Tracer 1.83 3.58 2.78
Solution with glycerin of Example 1 Invention 1.60 3.00 2.34
Solution Leak Tracer with high surfactant content - Composition B
Invention 2.23 3.65 3.05 Solution Leak Tracer with low surfactant
content - Composition A ______________________________________
It is seen from Table 2 above that the low surfactant content leak
tracer solution A of the invention showed the highest creepability
and efficiency of all three leak tracer solutions tested. In
addition, its low surfactant content renders it the most economical
to employ. Although the high surfactant content leak tracer
solution B of the invention had lower creepability than the leak
tracer solution containing glycerin, such high surfactant content
leak tracer solution has the above noted advantages over the
glycerin-containing presently employed leak tracer solution, in
avoiding formation of a gel-like growth within fuel tank lines, and
thus avoiding the clogging of passages therein, and also does not
stain the painted surfaces of aircraft with which it can come into
contact.
In the method for employing the leak tracer solution of the
invention to test for leaks in the fuel tanks and lines, e.g. of an
aircraft, the leak tracer solution is purged or introduced into
newly fabricated, clean and dry fuel tanks and lines. During the
test procedure, the leak tracer solution in the tanks and lines can
be at a pressure of say 5 psi, but the pressurization of the leak
tracer solution during testing is not necessary.
The external surfaces of the tanks and lines are inspected for
leaks while under suitable illumination, that is, either white
illumination where the dye in the leak tracer solution is a
daylight dye, or under black light illumination in dark enclosures
when the dye in the leak tracer solution is a fluorescent dye, or
has dual visibility. Particularly the fluorescent characteristics
of the fluorescent and dual visibility dyes are used to advantage
for locating minute leaks. After locating and marking the leaks
indicated by dye smears resulting from passage of leak tracer
solution through such leaks, the level of the leak tracer in the
tank or lines can be dropped sufficiently to permit repair of the
crack or leak, followed by retesting with the leak tracer solution
if desired, to verify the effectiveness of the repair.
Following inspection for leaks in the system, and any repairs
thereof, if desired, the leak tracer solution is drained from the
fuel tanks and lines to remove the leak tracer. In order to remove
any residual leak tracer solution which remains entrapped in
depressions or crevices of the fuel tanks and lines, a "depuddling"
agent is used after the draining of the main body of leak tracer
solution from the system. The depuddling agent employed is of a
unique type which chemically blends the water-based leak tracer
solution of the invention which remains entrapped within the
system, with the oil or petroleum-based aircraft fuel, which can
consist of saturated and/or unsaturated hydrocarbons, so that in
this manner, the remaining portions of the leak tracer solution are
leached out of the system. A typical depuddling agent for this
purpose is a mixture of a nonionic oxyalkylated aliphatic alcohol
of the types described above, with a petroleum based aircraft jet
fuel containing a mixture of hydrocarbons containing 6 to 16 carbon
atom chains, e.g. a 50--50 mixture, by volume, of Tergitol 15-S-5
and JP-4 jet fuel, consisting essentially of a mixture of 2 parts
of gasoline (6 to 8 carbon atom hydrocarbons) to 1 part of kerosene
(10 to 16 carbon atom hydrocarbons), by weight.
After the depuddling agent is introduced into the fuel tank and
lines, for removal of residual leak tracer solution, the resulting
miscible mixture of leak tracer solution and depuddling agent is
drained from the system. Any remaining residues of such mixture are
miscible with subsequently introduced petroleum-based fuel, and the
resulting mixture can be again drained from the system or burned
out by the aircraft engines during test runs prior to introduction
of the main body of fuel into the fuel tanks and lines for
operation of the aircraft.
The leak tracer solution removed from the tanks and lines following
testing, can be reused, and excess depuddling agent drained from
the tanks and lines also can be reused, if desired.
The above noted depuddling agent composition and its use in
combination with the leak tracer solution of the present
application, as described above, are disclosed and claimed in
applicant's copending application Ser. No. 66,608, filed Aug. 15,
1979.
The following are examples of the practice of the present
invention.
EXAMPLE 1
About 6500 gallons of a leak tracer solution was introduced into
the fuel tanks and lines of an aircraft in the "as painted" newly
fabricated condition. Such leak tracer solution contained, for 500
gallons of tap water, 2.5 gallons Tergitol 15-S-9, 1200 grams
Uranine Conc. 1801 dye and 20 gallons glycerin, corresponding by
weight, to about 0.5% Tergitol 15-S-9, about 5% glycerin, and about
0.03% Uranine Conc. 1801 dye, the remainder water. The external
surfaces of the tanks and lines were viewed under both white light
and black light, indicating the location of numerous leaks by the
yellow-green dye smears emitted by the uranine dye in the leak
tracer solution. Such leaks were marked, the leak tracer solution
was partially drained from the system, and the leaks thus located
were repaired.
Observations made after leak testing indicated that an undetermined
amount of the leak tracer solution remained entrapped (puddled)
inside the tanks and lines. Also, a film of glycerin stubbornly
adhered to the surfaces contacted by the solution. Apparently a
gel-like substance was entrapped in some fuel passages.
The leak tracer solution of the invention, Composition A, was
introduced into a system simulating the fuel tanks and lines noted
above, and having painted surfaces. The external surfaces of the
equipment were viewed under white and black light, indicating the
location of numerous leaks by the yellow-green dye smears emitted
by the leaking solution. The leaks were marked, the leak tracer
solution was drained from the system, and the leaks thus located
were repaired.
The above noted depuddling agent, consisting of 50 parts of
Tergitol 15-S-5 and 50 parts of JP-4 Petroleum-based jet fuel, by
volume, was introduced into the tanks and lines of the above
simulated system to remove any remaining portions of the leak
tracer solution, Composition A, and the resulting mixture of
depuddling agent and residual leak tracer solution, was
removed.
Although considerable wetting of the painted outside surfaces of
the simulated aircraft tanks and lines took place as a result of
the use of the leak tracer solution, Composition A, no staining of
the painted surfaces resulted, and there was no contamination, that
is, no formation of a sticky film such as formed by the glycerin in
the above noted formulation, on the surfaces wetted by the
solution, and there was no evidence of a gel-like substance
entrapped in the system.
EXAMPLE 2
Results similar to those of Example 1 were obtained employing in
place of the leak tracer solution, Composition A, the respective
leak tracer colutions C, D, E, F and J above.
EXAMPLE 3
The procedure of Example 1 is repeated, but employing the
respective leak tracer solutions B, G and H of Table 1 above, in
place of leak tracer solution or Composition A.
Results comparable to those of Example 1 were obtained; however, it
was noted that when employing leak tracer solutions B, G and H
containing a high surfactant content as noted above, the dye smears
and indications of cracks and leaks when the system was subjected
to ultraviolet light, were not as sharp and definitive as in the
case of the leak tracer solution of Example 1.
From the foregoing it is seen that the invention of the present
application provides an improved leak tracer solution having a
number of important advantages. The characteristics and advantages
afforded by the leak tracer solution and process employing same of
the invention include (1) economy of manufacture, (2)
nonflammability of the leak tracer solution, (3) non-staining to
painted surfaces, (4) quick action of the leak tracer solution in
detecting leaks when exposed to suitable lighting conditions such
as white light and/or black light illumination, (5) dual
visibility, (6) non-toxicity of the leak tracer solution, which
evolves no fumes or odor, and its very high water content makes it
dermatologically and environmentally safe, and (7) the remaining
entrapped solution following testing can be removed or depuddled.
The non-clogging characteristics of the leak tracer solution
assures safe and efficient operation of the aircraft following the
leak detection procedure. Finally, the leak tracer solution can be
readily and efficiently eliminated from the fuel tanks and lines
following the testing procedure, particularly by use of a suitable
"depuddling" agent, and parasitic growth in the leak tracer
solution can be readily controlled by use of anti-parasitic
agents.
Although the leak tracer solution of the invention, with its
preferred non-staining characteristics with respect to painted
surfaces, is usually applied to fuel tanks and lines which have
been installed in a painted aircraft, the solution can also be used
advantageously for detecting leaks in such systems before they have
been installed in a painted aircraft. Either or both the exterior
surfaces of the fuel tank and of the adjacent structural components
of the aircraft such as the wings can be painted, and the leak
tracer solution can come into contact with such painted surfaces by
accidental spillage or through leaks, without staining such
surfaces.
Since various changes and modifications of the invention will occur
to and can be made readily by those skilled in the art without
departing from the invention concept, the invention is not to be
taken as limited except by the scope of the appended claims.
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